A continuing goal of integrated circuit fabrication is to decrease the dimensions thereof. Integrated circuit dimensions can be decreased by reducing the dimensions and spacing of the constituent features or structures thereof For example, by decreasing the dimensions and spacing of features (e.g., storage capacitors, access transistors, access lines) of a memory device, the overall dimensions of the memory device may be decreased while maintaining or increasing the storage capacity of the memory device.
Reducing the dimensions and spacing of semiconductor device features places ever increasing demands on the methods used to form the features. For example, due to limitations imposed by optics and radiation wavelengths, many conventional photolithographic methods cannot facilitate the formation of features having critical dimensions (e.g., widths, diameters) of less than about forty (40) nanometers (nm). Electron beam (E-beam) lithography and extreme ultraviolet (EUV) lithography have been used to form features having critical dimensions less than 40 nm, but generally require complex processes and significant costs.
One approach for achieving semiconductor device features having critical dimensions of less than about 40 nm has been patterning using chemical pattern-directed self-assembly (e.g., chemoepitaxy) of a block copolymer material, wherein a patterned template material is used to direct the self-assembly of a block copolymer material to form domains of a polymer block of a block copolymer distinct from domains of another polymer block of the block copolymer. A preferential wetting affinity of the patterned template material for one of the polymer blocks of the block copolymer directs the self-assembly of the distinct domains in accordance with the patterned template material. The domains of the polymer block or the domains of the another polymer block can be selectively removed, and the remaining domains can be utilized as desired (e.g., as an etch mask for patterning features into an underlying substrate or material). As the dimensions of the distinct domains are at least partially determined by the chain length of the block copolymer, feature dimensions much smaller than 40 nm are achievable (e.g., dimensions similar to those achievable through E-beam and EUV lithography processes).
Unfortunately, conventional methods of forming the patterned template material utilized for the chemical pattern directed self-assembly of the block copolymer material can suffer from a variety of problems. For instance, one conventional method includes foiniing a positive tone photoresist material over a template material, exposing the positive tone photoresist to radiation, removing photoexposed regions of the positive tone photoresist material with a positive tone developer to form a patterned photoresist material, removing portions of the patterned photoresist material and the template material using a plasma of oxygen (O2), chlorine (Cl2), and hydrogen (H2), and removing remaining portions of the patterned photoresist material using a negative tone developer. Such a method can be inefficient and cost-prohibitive due to the limited number of plasma and developer chemistries suitable for use with the method. For example, negative tone developers suitable for removing the patterned photoresist material generally include hazardous materials, such as dimethyl sulphoxide (DMSO), that necessitate the use of separate, specialized, and costly equipment and processes to mitigate health, safety, and environmental concerns, and equipment longevity concerns related to the use of such hazardous materials.
A need, therefore, exists for new, simple, and cost-efficient methods of forming semiconductor device structures and patterned template materials for use in chemical pattern directed self-assembly of block copolymer materials. It would be further desirable if the methods were compatible with a wide variety of conventional tools, processes, and materials.